A protective film may be used to prevent an attachment of debris such as dusts or generation of scratches in optical films, such as a polarizing plate, other plastic products, home appliances, or automobiles. Proper peel strength and an antistatic property are required in the protective film.
For instance, relatively low peel strength is required when peeling the protective film off at a high speed (hereinafter, “high-speed peel strength”) in order to use the product or assemble other products. On the other hand, the peel strength upon peeling off at a low speed (hereinafter, “low-speed peel strength”) may be relatively high so that it can exhibit a proper protection function.
In addition, the static electricity mainly generated upon peeling the protective film may induce an influx of impurities, such as dust, or electrostatic destruction or malfunction of a device in the case of electronic products. Especially, issues caused by static electricity are becoming more severe as more computers are supplied and as the appliances are further integrated by multi-functionalization of liquid crystal TVs or mobile phones.
As such, efforts to impart an antistatic function to an adhesive contained in the protective film are ongoing.
For example, suppression of static electricity generation was attempted by combining an adhesive with an ethylene oxide-modified dioctyl phthalate plasticizer in Patent Literature 1. Addition of an organic salt to an adhesive was attempted in Patent Literature 2, and a metal salt and a chelating agent were combined in an adhesive in Patent Literature 3. However, according to these methods, contamination occurs by a transfer of adhesive components to the product to be protected, or suppression of static electricity generated in early stage is difficult, and particularly the low-speed peel strength which is important for the protection function becomes too low.